Removal of methyl orange from wastewater using sustainable and facilely synthesized weathered
Ali M El Shafey1, Mahmoud S M Abdel Wahed2, Ahmed M Zayed3
1Department of Chemistry, Faculty of Science, Beni-Suef University, Beni-Suef, Egypt.
Abstract:
A sustainable strategy was developed to synthesize high-performance adsorbents by integrating raw (RWB) and calcined (CWB) weathered basalt with chitosan and polyaniline via in situ oxidative polymerization. The resulting ternary composites (RWB/Ch/PANI and CWB/Ch/PANI) were characterized using XRD, FTIR, SEM, TEM, and BET analyses, confirming successful polymer incorporation and the formation of hierarchical nanostructures. RWB/Ch/PANI exhibited more uniform nanofibers and superior surface functionality due to the amorphous, clay-rich nature of RWB, whereas CWB/Ch/PANI showed spheroidal domains related to its crystalline precursor. Under optimized conditions (pH 4, 200 mg/50 mL, 100 mg L-1, 40 min, 300 rpm), both composites achieved >97 % methyl orange (MO) removal. Kinetic analysis followed the pseudo-second-order (PSO) model, with close agreement between experimental (qₑexp = 32.67 and 32.47 mg g-1) and calculated values (qₑcal = 33.6 mg g-1), confirming chemisorption as the rate-limiting step. Isotherm fitting indicated that the Freundlich model best described the process (R2 ≈ 0.99; χ2 = 0.47 for RWB/Ch/PANI and 0.19 for CWB/Ch/PANI), suggesting multilayer adsorption on heterogeneous surfaces. Mechanistic analysis revealed that electrostatic attraction, hydrogen bonding, and π-π stacking governed MO uptake, with electrostatic forces dominating under acidic conditions. Notably, RWB/Ch/PANI achieved comparable performance to CWB/Ch/PANI without energy-intensive calcination, offering a greener, cost-effective, and scalable approach for dye-laden wastewater treatment.
